摘要：We have used tide-gauge data from near Helheim Glacier, East Greenland, and GPS data acquired on the glacier to investigate the spectra of tidal forcing and flow response. For both the tide-gauge and GPS time series, we calculated amplitudes and phases for a harmonic expansion using a limited set of harmonic constituents. We find that the semidiurnal constituents of the glacier flow are well modeled using a single admittance and lag with respect to the tide-gauge data. However, diurnal variations in the glacier flow cannot be simply described using this model. We find an additional signal in glacier position, in phase with the S 1 solar tide, with some modulations at other frequencies. These non-tidal variations account for a peak-to-peak variation in glacier flow speed at a site close to the terminus of ~0.7 m d -1 , compared with a mean flow rate at this location of ~22 m d -1 . The speed variations reach their daily maximum value ~6 hours after local noon. We hypothesize that these additional diurnal variations are associated with peaks in lubrication of the glacier bed due to surface melting driven by diurnal solar heating.
